Does activating a Tentacle Rod break the invisibility spell?

Question

The Invisibility spell ends when the target attacks or casts a spell:

The spell ends for a target that attacks or casts a spell.

The "Tentacle Rod" magical items lets the user direct three tentacles to attack target(s):

While holding the rod, you can use an action to direct each tentacle to attack a creature you can see within 15 feet of you. Each tentacle makes a melee attack roll with a +9 bonus. On a hit, the tentacle deals 1d6 bludgeoning damage. If you hit a target with all three tentacles, it must make a DC 15 Constitution saving throw. On a failure, the creature's speed is halved, it has disadvantage on Dexterity saving throws, and it can't use reactions for 1 minute.

Does activating the Tentacle Rod break the invisibility spell? I'm not sure if "directing each tentacle to attack" counts as attacking yourself.

Answer 1

RAW, I would rule that the Tentacle Rod (and its wielder) remain invisible.

Invisibility states:

A creature you touch becomes invisible until the spell ends. [...] The spell ends for a target that attacks or casts a spell. (PHB, pg. 254)

The "target" of invisibility is the creature you touch. Invisibility ends when that target attacks or casts a spell.

The description of the Tentacle Rod is quite clear - the tentacles are making the attacks:

While holding the rod, you can use an action to direct each tentacle to attack a creature you can see within 15 feet of you. Each tentacle makes a melee attack roll with a +9 bonus. On a hit, the tentacle deals 1d6 bludgeoning damage. (DMG, pg. 208)

The Tentacle Rod is not the target of invisibility, so invisibility does not end when the tentacles attack.

If it were the cast the the wielder were the one making the attacks with the tentacles, I would expect the language to be more similar to something like scorching ray:

Make a ranged spell attack for each ray.

For me, to rule this the other way, the description for the tentacle attacks would have to have said something like:

Make a melee attack for each tentacle, using +9 to hit.

Worded this way, it’s clear the wielder is making the attack.

Answer 2

Yes.

Invisibility says:

Anything the target is wearing or carrying is invisible as long as it is on the target's person

I'd propose that this is a case (like fireball) where a spell uses "target" to refer to something affected by the spell, whether or not it's strictly the target.

Usually it wouldn't matter, because things carried by the invisible creature can't attack or cast spells on their own.

A case where it does matter is when the creature is carrying another creature. For example, you've got a half-orc barbarian with 18 Strength ("Blaster"), and a halfling sorcerer who rides on his shoulders ("Master"). Master casts invisibility on Blaster. Since Blaster is carrying Master, they both turn invisible.

Now, if you interpret invisibility's "target" as only referring to Blaster, then Master can sit up there and chuck fire bolts at their enemies all they want while staying invisible. This is clearly unbalanced and contrary to the intended function of the spell. Reasonably, we have to interpret "target" as meaning the targeted creature and anything they are wearing or carrying. If something they're carrying makes an attack, then the spell breaks.

The same logic applies to the Tentacle Rod. Assuming its tentacles benefit from invisibility in the first place (since it's debatable whether they're on your person), they will break the spell when they attack.